The present invention relates to a method of casting an article, such as an airfoil, having an internal space. The article may be formed by a lost wax investment casting process.
Airfoils have previously been cast by providing cores having configurations corresponding to the configuration of passages to be formed in the airfoils. The core is enclosed by wax to form a mold cavity pattern having a configuration corresponding to the configuration of the airfoil. The wax is removed from a portion of the core to form areas, commonly referred to as core prints, where portions of the core are exposed.
To form the core prints, wax has previously been removed by using a scalpel to cut away the wax from the core. Edges of the wax are sealed using a hot needle. The process of removing the wax using a scalpel and sealing the edges of the wax with a hot needle is very labor-intensive. In addition, the delicate ceramic cores may be damaged during cutting away of the wax and sealing of the wax.
Once the core prints have been formed, the pattern is covered with ceramic mold material. The ceramic mold material engages the exposed portion of the core at the core prints. After the ceramic mold material has at least partially set, the wax material is removed by heating the mold. This leaves a mold cavity having a configuration corresponding to the configuration of the airfoil to be cast. The ceramic mold material engages the core to hold the core at the areas where the mold material was previously exposed by removing the wax pattern, for example, at the core prints.
Molten metal is then poured into the mold cavity, the molten metal solidifies to form the airfoil. After the molten metal solidifies, the airfoil is removed from the mold and the core material is removed from inside of the airfoil. This leaves passages inside the airfoil to conduct a flow of cooling fluid. These passages have a configuration which corresponds to the configuration of the core.
The present invention relates to a new and improved method of casting an article having an internal space by a lost wax casting process. The article may be a metal airfoil with an internal passage.
A core is provided. The core has a configuration corresponding to the space in the article. If the article is an airfoil, the core may have a configuration corresponding to the configuration of a passage in the airfoil. The core is at least partially enclosed with a layer of wax.
A portion of the wax layer is removed from the core. A mold is formed by at least partially coating the wax layer with mold material. The wax layer is removed from the mold to form a mold cavity. The mold cavity is filled with a flowable material, such as molten metal, which engages the core to form the internal space in the cast article.
A portion of the wax layer is removed from the core by heating a tubular member. The heated tubular member engages the wax layer to melt a portion of the wax layer. Melted wax is conducted away from the core through the heated tubular member.